Re: Performance difference in accessing differrent columns in a Postgres Table

Ok, will do that. Thanks a lot.

On Wed, Sep 5, 2018 at 9:37 PM Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:

>
>
> On Wed, Sep 5, 2018 at 12:00 PM Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
>
>> On Wed, Sep 5, 2018 at 12:21 AM Dinesh Kumar <dns98944(at)gmail(dot)com> wrote:
>>
>>> Hi All,
>>> I was wondering whether the case is solved or still continuing. As a
>>> Postgres newbie, I can't understand any of the terms (JIT, tuple
>>> deformation) as you mentioned above. Please anyone let me know , what is
>>> the current scenario.
>>>
>>>
>> JIT is a just-in-time compilation, which will be new in v11. Tuple
>> deforming is how you get the row from the on-disk format to the in-memory
>> format.
>>
>> Some people see small improvements in tuple deforming using JIT in your
>> situation, some see large decreases, depending on settings and apparently
>> on hardware. But regardless, JIT is not going to reduce your particular
>> use case (many nullable and actually null columns, referencing a
>> high-numbered column) down to being constant-time operation in the number
>> of preceding columns. Maybe JIT will reduce the penalty for accessing a
>> high-numbered column by 30%, but won't reduce the penalty by 30 fold. Put
>> your NOT NULL columns first and then most frequently accessed NULLable
>> columns right after them, if you can.
>>
>
> Correction: NOT NULL columns with fixed width types first. Then of the
> columns which are either nullable or variable width types, put the most
> frequently accessed earlier.
>
>